A comprehensive collection of results on longitudinal double-spin asymmetries is presented for charged pions and kaons produced in semi-inclusive deep-inelastic scattering of electrons and positrons ...on the proton and deuteron, based on the full HERMES data set. The dependence of the asymmetries on hadron transverse momentum and azimuthal angle extends the sensitivity to the flavor structure of the nucleon beyond the distribution functions accessible in the collinear framework. No strong dependence on those variables is observed. In addition, the hadron charge-difference asymmetry is presented, which under certain model assumptions provides access to the helicity distributions of valence quarks.
A measurement of beam-helicity asymmetries for single-hadron production in deep-inelastic scattering is presented. Data from the scattering of 27.6 GeV electrons and positrons off gaseous hydrogen ...and deuterium targets were collected by the HERMES experiment. The asymmetries are presented separately as a function of the Bjorken scaling variable, the hadron transverse momentum, and the fractional energy for charged pions and kaons as well as for protons and anti-protons. These asymmetries are also presented as a function of the three aforementioned kinematic variables simultaneously.
Observation of the decay Λb0→ χc1pπ Alexander, M.; An, L.; Basels, J. M. ...
The journal of high energy physics,
05/2021, Letnik:
2021, Številka:
5
Journal Article
Recenzirano
Odprti dostop
A
bstract
The Cabibbo-suppressed decay
Λ
b
0
→
χ
c1
pπ
−
is observed for the first time using data from proton-proton collisions corresponding to an integrated luminosity of 6 fb
−
1
, collected with ...the LHCb detector at a centre-of-mass energy of 13 TeV. Evidence for the
Λ
b
0
→
χ
c2
pπ
−
decay is also found. Using the
Λ
b
0
→
χ
c1
pK
−
decay as normalisation channel, the ratios of branching fractions are measured to be
B
Λ
b
0
→
χ
c
1
pπ
−
B
Λ
b
0
→
χ
c
1
pK
−
=
6.59
±
1.01
±
0.22
×
10
−
2
,
B
Λ
b
0
→
χ
c
2
pπ
−
B
Λ
b
0
→
χ
c
1
pπ
−
=
0.95
±
0.30
±
0.04
±
0.04
,
B
Λ
b
0
→
χ
c
2
pK
−
B
Λ
b
0
→
χ
c
1
pK
−
=
1.06
±
0.05
±
0.04
±
0.04
,
where the first uncertainty is statistical, the second is systematic and the third is due to the uncertainties in the branching fractions of χ
c1
,
2
→
J
/
ψγ decays.
We report a measurement of time-dependent CP violation parameters in B0→KS0ηγ decays. The study is based on a data sample, containing 772×106BB¯ pairs, that was collected at the ϒ(4S) resonance with ...the Belle detector at the KEKB asymmetric-energy e+e− collider. We obtain the CP violation parameters of S=−1.32±0.77(stat)±0.36(syst) and A=−0.48±0.41(stat)±0.07(syst) for the invariant mass of the KS0η system up to 2.1 GeV/c2.
Observation of the Decay Bs0 → K0 K ¯ 0 Schwartz, A. J.; Aihara, H.; Ayad, R. ...
Physical review letters,
04/2016, Letnik:
116, Številka:
16
Journal Article
Recenzirano
Odprti dostop
We measure the decay B$^{0}_{s}$ → K0K¯0 using data collected at the Υ(5S) resonance with the Belle detector at the KEKB e+e– collider. The data sample used corresponds to an integrated luminosity of ...121.4 fb–1. We measure a branching fraction B(B$^{0}_{s}$ → K0K¯0) = 19.6$^{+5.8}_{–5.1}$(stat.) ± 1.0(sys.)±2.0(NB$^{0}_{s}$B¯$^{0}_{s}$)×10–6 with a significance of 5.1 standard deviations. Here, this measurement constitutes the first observation of this decay.
Observation of the Bs0 → D±D∓ decay Alexander, M.; Baryshnikov, F.; Belov, I. ...
The journal of high energy physics,
03/2021, Letnik:
2021, Številka:
3
Journal Article
Recenzirano
Odprti dostop
A
bstract
A search for the
B
s
0
→ D
*±
D
∓
decay is performed using proton-proton collision data at centre-of-mass energies of 7, 8 and 13 TeV collected by the LHCb experiment, corresponding to an ...integrated luminosity of 9 fb
−
1
. The decay is observed with a high significance and its branching fraction relative to the
B
0
→ D
*±
D
∓
decay is measured to be
ℬ
B
s
0
→
D
∗
±
D
∓
B
0
→
D
∗
±
D
∓
=
0.137
±
0.017
±
0.002
±
0.006
,
where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the ratio of the
B
s
0
and
B
0
hadronisation fractions.
A
bstract
The first full angular analysis of the
B
0
→
D
∗
−
D
s
∗
+
decay is performed using 6 fb
−
1
of
pp
collision data collected with the LHCb experiment at a centre-of-mass energy of 13 TeV. ...The
D
s
∗
+
→
D
s
+
γ
and
D
*
−
→
D
¯
0
π
−
vector meson decays are used with the subsequent
D
s
+
→
K
+
K
−
π
+
and
D
¯
0
→
K
+
π
−
decays. All helicity amplitudes and phases are measured, and the longitudinal polarisation fraction is determined to be
f
L
= 0
.
578 ± 0
.
010 ± 0
.
011 with world-best precision, where the first uncertainty is statistical and the second is systematic. The pattern of helicity amplitude magnitudes is found to align with expectations from quark-helicity conservation in
B
decays. The ratio of branching fractions ℬ(
B
0
→
D
∗
−
D
s
∗
+
) × ℬ(
D
s
∗
+
→
D
s
+
γ
)
/
ℬ(
B
0
→
D
*
−
D
s
+
) is measured to be 2
.
045 ± 0
.
022 ± 0
.
071 with world-best precision. In addition, the first observation of the Cabibbo-suppressed
B
s
→
D
*
−
D
s
+
decay is made with a significance of seven standard deviations. The branching fraction ratio ℬ(
B
s
→
D
*
−
D
s
+
)
/
ℬ(
B
0
→
D
*
−
D
s
+
) is measured to be 0
.
049 ± 0
.
006 ± 0
.
003 ± 0
.
002, where the third uncertainty is due to limited knowledge of the ratio of fragmentation fractions.
A
bstract
Measurements of
CP
observables in
B
±
→
DK
±
and
B
±
→
Dπ
±
decays are presented, where
D
represents a superposition of
D
0
and
D
¯
0
states. The
D
meson is reconstructed in the three-body ...final states
K
S
0
K
±
π
∓
and
K
S
0
K
∓
π
±
. The analysis uses samples of
B
mesons produced in proton-proton collisions, corresponding to an integrated luminosity of 1.0, 2.0, and 6.0 fb
−
1
collected with the LHCb detector at centre-of-mass energies of
s
= 7, 8, and 13 TeV, respectively. These measurements are the most precise to date, and provide important input for the determination of the CKM angle
γ
.
Single-spin asymmetries were investigated in inclusive electroproduction of charged pions and kaons from transversely polarized protons at the Hermes experiment. The asymmetries were studied as a ...function of the azimuthal angle ψ about the beam direction between the target-spin direction and the hadron production plane, the transverse hadron momentum PT relative to the direction of the incident beam, and the Feynman variable xF. The sinψ amplitudes are positive for π+ and K+, slightly negative for π− and consistent with zero for K−, with particular PT but weak xF dependences. Especially large asymmetries are observed for two small subsamples of events, where also the scattered electron was recorded by the spectrometer.
A
bstract
Measurements of
CP
observables in
B
±
→
D
(*)
K
±
and
B
±
→
D
(*)
π
±
decays are presented, where
D
(∗)
indicates a neutral
D
or
D
∗
meson that is an admixture of meson and anti-meson ...states. Decays of the
D
(∗)
meson to the
Dπ
0
and
Dγ
final states are partially reconstructed without inclusion of the neutral pion or photon. Decays of the
D
meson are reconstructed in the
K
±
π
∓
,
K
+
K
−
, and
π
+
π
−
final states. The analysis uses a sample of charged
B
mesons produced in proton-proton collisions and collected with the LHCb experiment, corresponding to integrated luminosities of 2.0, 1.0, and 5.7 fb
−
1
taken at centre-of-mass energies of 7, 8, and 13 TeV, respectively. The measurements of partially reconstructed
B
±
→
D
(*)
K
±
and
B
±
→
D
(∗)
π
±
with
D
→
K
∓
π
±
decays are the first of their kind, and a first observation of the
B
±
→
D
π
0
D
∗
π
±
decay is made with a significance of 6.1 standard deviations. All
CP
observables are measured with world-best precision, and in combination with other LHCb results will provide strong constraints on the CKM angle
γ
.
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